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The Science Of Hydration

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== Caffeine and Alcohol ==
The scientific evidence shows that caffeine is generally not a diuretic <ref name="ref5"/><ref name="ref14"/><ref name="ref15"/>. Previous studies have shown that if you don't normally take caffeine and then get a large dose, there is some diuretic effect. However normal intakes of caffeine by non-users and use by regular users is not a diuretic <ref name="ref16"/>. (If you urinate more because you drink a 20oz Latte, it is because of the 20oz of fluid, not the caffeine.)
Alcohol is another story; drinking anything stronger than 2% will cause dehydration. Because alcohol takes 36 hours to clear the body, it should be avoided for 48 hours before you wish to avoid impaired performance <ref name="ref5"/>.
== Muscle Cramps ==
== Blisters and black toe nails ==
Dehydration reduces body weight, which can reduce the size of your feet. This in turn changes the fit of your shoes, causing blisters. Hyponatremia can cause swelling, which increases the size of your feet and can cause blisters. Both conditions can also increase the chance of black toe nails.
==Water in the Body<ref name="CLINC"/>==
Approximately 60% of the human body weight is water, though this varies primarily with body fat as adipose (fat) tissue contains a lower percentage of water. Total Body Water (TBW) can be divided up into
* Intracellular fluid (ICF) which is 40% of body weight
* Extracellular fluid (ECF) which is the other 20% of body weight
** plasma is 25% of ECF/5% body weight
** interstitial fluid which is 75% of ECF/15% of body weight, typically 11 Liters/22 pints.
==Symptoms of Dehydration<ref name="CLINC"/>==
These symptoms are for the general public, and there is evidence<ref name="SYMPT"/> that they may not apply to athletes suffering from mild dehydration
{| {{table}}
| align="center" style="background:#f0f0f0;"|'''symptom'''
| align="center" style="background:#f0f0f0;"|'''mild dehdration (3-5% body weight)'''
| align="center" style="background:#f0f0f0;"|'''Moderate dehdration (6-9% body weight)'''
| align="center" style="background:#f0f0f0;"|'''Severe dehdration (>10% body weight)'''
| Level of consciousness||Alert ||Lethargic ||Obtunded
| Capillary Refill||2 seconds||2-4 seconds||>4 seconds
| Blood Pressure||Normal||Normal supine, lower standing||lower
| Skin Turgor||Normal||Slow||Tenting
| Eyes||Normal||Sunken||Very Sunken
== References ==
<ref name="CLINC">Clinical Studies in Fluid and Electrolyte Balance</ref>
<ref name="SYMPT">Sensitivity and specificity of clinical signs for assessment of dehydration in endurance athletes
<ref name="ref1">Exercise-Associated Hyponatremia

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